A K-band integrated bandpass filter in 90-nm CMOS technology

This paper investigates the design and implementation of integrated bandpass filters in standard 90-nm CMOS technology for K-band applications. A Chebyshev bandpass filter with a measured 7% 1-dB bandwidth at 20 GHz is realized using lumped-element components. Meander-line inductors are implemented using the thick metallization layer of the CMOS process to improve the filter quality factor. Metal-insulator-metal (MIM) capacitors are implemented using the thin SiO₂ layer of the process to reduce the size of the filter. The effect of dense metal filling is considered in full-wave simulations to predict the filter response after fabrication. Measurement results show an insertion loss of 5 dB, a return loss better than 10 dB and an unloaded quality factor of 12.5 for the bandpass filter at 20 GHz. The reported filter is at least 10 times smaller compared to the equivalent microstrip-based filter at K-band frequency.